RE: The Need For Speed!!!
I agree with Bob, some of the Jetts and Nelsons I've seen on the auction site I wouldn't touch.
I've sold 5 or 6 Nelsons there over the past year or so, and you use to get $225 for a good used motor, but now its down closer to $150. I've kept the few short strokes I have left and will sell them to any local that is interested in moving up to that racing class.
I use primarily Nelsons for racing, but love the sport jetts, and have them on all of my sport planes. Great idle, transition, and unload. Tough to beat. A 428 nelson will only be happy spinning over 19k, so I don't see it as a great option for most sport planes.